import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;

public class BinaryTree {


    static class TreeNode {
        @Override
        public String toString() {
            return "TreeNode{" +
                    "val=" + val +
                    ", left=" + left +
                    ", right=" + right +
                    '}';
        }

        public char val;
        public TreeNode left;//左孩子的引用
        public TreeNode right;//右孩子的引用

        public TreeNode(char val) {
            this.val = val;
        }
    }
    public TreeNode root;

    /**
     * 创建一棵二叉树 返回这棵树的根节点
     *
     * @return
     */
    public TreeNode createTree() {

        TreeNode A = new TreeNode('A');
        TreeNode B = new TreeNode('B');
        TreeNode C = new TreeNode('C');
        TreeNode D = new TreeNode('D');
        TreeNode H = new TreeNode('H');
        A.left = B;
        A.right = C;
        B.left = D;
        B.right = H;
        root = A;
        return  root;
    }

    // 前序遍历
    public void preOrder(TreeNode root) {
        if(root == null){
            return;
        }
        System.out.print(root.val+" ");
        preOrder(root.left);
        preOrder(root.right);
    }

    // 中序遍历
    void inOrder(TreeNode root) {
        if(root == null){
            return;
        }
        preOrder(root.left);
        System.out.print(root.val+" ");
        preOrder(root.right);
    }

    // 后序遍历
    void postOrder(TreeNode root) {
        if(root == null){
            return;
        }
        preOrder(root.left);
        preOrder(root.right);
        System.out.print(root.val+" ");

    }

    public static int nodeSize;

    /**
     * 获取树中节点的个数：遍历思路
     */
    void size(TreeNode root) {
        if(root == null){
            return;
        }
        nodeSize++;
        size(root.right);
        size(root.left);

    }

    /**
     * 获取节点的个数：子问题的思路
     *
     * @param root
     * @return
     */
    int size2(TreeNode root) {
        if (root == null){
            return 0;
        }
        int left = 0;
        left = size2(root.left);
        int right = 0;
        right = size2(root.right);
        return left + right + 1;
    }


    /*
     获取叶子节点的个数：遍历思路
     */
    public static int leafSize = 0;

    void getLeafNodeCount1(TreeNode root) {
        if(root == null){
            return;
        }
        if (root.left == null && root.right == null){
            leafSize++;
        }
        getLeafNodeCount1(root.right);
        getLeafNodeCount1(root.left);

    }

    /*
     获取叶子节点的个数：子问题
     */
    int getLeafNodeCount2(TreeNode root) {
        if (root == null){
            return 0;
        }
        if (root.right == null && root.left == null){
            return 1;
        }
        return getLeafNodeCount2(root.left)+getLeafNodeCount2(root.right);
    }

    /*
    获取第K层节点的个数
     */
    int getKLevelNodeCount(TreeNode root, int k) {
        if ( root == null){
            return 0;
        }
        if (k == 1){
            return  1;
        }
        return (getKLevelNodeCount(root.left,k-1)+getKLevelNodeCount(root.right,k-1));

    }

    /*
     获取二叉树的高度
     时间复杂度：O(N)
     */
    int getHeight(TreeNode root) {
    if (root == null) {
        return 0;
    }
    return Math.max(getHeight(root.left),getHeight(root.right)) + 1;
    }


    // 检测值为value的元素是否存在
    TreeNode find(TreeNode root, char val) {
        if (root == null){
            return null;
        }
        if (root.val == val){
            return root;
        }
        TreeNode left = find(root.left,val);
        if (left != null){
            return left;
        }
        TreeNode right = find(root.right,val);
        if (right != null){
            return right;
        }
        return null;
    }

    //层序遍历
    void levelOrder(TreeNode root) {
        if(root == null){
            return;
        }
        Queue<TreeNode> queue = new LinkedList<>();

        queue.offer(root);

        while(!queue.isEmpty()){
            TreeNode cur = queue.poll();
            System.out.print(cur.val+" ");
            if(cur.left != null){
                queue.offer(cur.left);
            }
            if(cur.right != null){
                queue.offer(cur.right);
            }
        }
    }
    //用二维数组的方式打印
//
//    class Solution {
//        public List<List<Integer>> levelOrder(TreeNode root) {
//
//            List<List<Integer>> list = new ArrayList<>();
//            if(root == null){
//                return list;
//            }
//            Queue<TreeNode> queue = new LinkedList<>();
//
//            queue.offer(root);
//
//            while(!queue.isEmpty()){
//                int size = queue.size();
//                List<Integer> list1 = new ArrayList<>();
//
//
//                while(size > 0) {
//                    TreeNode cur = queue.poll();
//                    list1.add(cur.val);
//                    if (cur.left != null) {
//                        queue.offer(cur.left);
//                    }
//                    if (cur.right != null) {
//                        queue.offer(cur.right);
//                    }
//                    size--;
//                }
//                list.add(list1);
//            }
//            return  list;
//        }
//    }

    // 判断一棵树是不是完全二叉树
    boolean isCompleteTree(TreeNode root) {
        if (root == null){
            return false;
        }
        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(root);

        while (!queue.isEmpty()){
            TreeNode cur  = queue.poll();
            if (cur != null  ){
                queue.offer(cur.left);
                queue.offer(cur.right);
            }
            else {
                break;
            }
        }
        while(!queue.isEmpty()){
            TreeNode node = queue.poll();
            if (node != null){
                return  false;
            }

        }
        return true;
    }
}
